If image data is generated by reading printed matter with an image sensor, halftone dots in the printed matter appear in the image represented by this image data. When processing the image data to identify character pixels in the image, pixels constituting halftone dots are often misidentified as character pixels.
A conventional image processing apparatus executes an edge determination for each pixel of an image to determine whether the pixel represents an edge, and a halftone dot determination for each pixel to determine whether the pixel represents a halftone dot. The image processing device identifies pixels that are edges but not halftone dots as pixels representing a character (i.e., text).